Effect of Component Impulsive Loading on Relative ACL Strain

描述（申请人提供）：膝关节前交叉韧带（ACL）损伤经常改变运动者的生活方式。最近，无论选择何种治疗方法，这些损伤的长期后果已经变得更加清晰。退行性关节炎是最常见的结果，发生在损伤后7年内（Pinczewski 2002）。据估计，2005年美国有30万ACL撕裂手术治疗（AOSSM 2006），因此有必要更好地预防这些伤害。这一建议解决了迫切需要更好地了解前交叉韧带损伤的机制，希望改善危险因素的监测和预防方案。许多前交叉韧带损伤发生在单脚起跳或奔跑和切割时。对于脉冲载荷方向对前交叉韧带应变的影响，目前还没有系统的研究。我们计划使用尸体结构，首先确定对膝关节施加压缩和力矩的脉冲载荷方向如何影响前交叉韧带应变。膝关节最初将通过拉伸四头肌、内侧和外侧腘绳肌和腓肠肌，以15°的初始角度进行约束，但膝关节在负荷下可以弯曲。在AIM 1中，我们将验证一个假设，即与矢状对称载荷相比，施加外翻、内部或外部轴向旋转力矩的2*BW脉冲力会增加前交叉韧带应变峰值。在AIM 2中，我们将检验AIM 1外翻和轴向旋转力矩分量的叠加导致ACL应变峰值大于相似幅度的弯曲力矩的假设。在AIM 3中，假设将被验证，在4*BW脉冲载荷下，非矢状面载荷组件比矢状对称载荷组件有更高的ACL破裂风险。在AIM 4中，我们将验证这样的假设，即当膝关节在脉冲负荷下屈曲时，腘绳肌的拉伸可以减少前交叉韧带的峰值应变。试点数据表明，这种拉伸可以诱导当足够的髋关节屈曲伴随膝关节屈曲与跳跃着陆；缺乏这种拉伸会导致前交叉韧带劳损增加。三个假设将在重复测量设计中使用成对的膝盖进行测试。负载传感器将用于测量膝盖上下的三维脉冲载荷，肌肉力将使用负载传感器测量。使用Certus系统测量股骨和胫骨的三维运动学。ACL相对应变将使用差分可变磁阻传感器进行测量。将使用多达120具尸体的膝盖。

DESCRIPTION (provided by applicant): Anterior cruciate ligament (ACL) injuries of the knee frequently alter the lifestyle of active people. Recently, the long-term consequences of these injuries have become clearer regardless of the treatment chosen. Degenerative arthritis is the most common outcome, occurring in as little as seven years post injury (Pinczewski 2002). With an estimated 300,000 ACL tears surgically treated in the U.S. in 2005 (AOSSM 2006) there is a need to better prevent these injuries. This proposal addresses the urgent need to better understand the mechanism of ACL injury in hopes of improving both risk factor surveillance and prevention programs. Many ACL injuries occur when landing on one foot from a jump or when running and cutting. There are no systematic studies of how the direction of the impulsive loading affects ACL strain. We plan to use a cadaver construct to first determine how ACL strain is affected by the direction of an impulsive load that applies both compression and a moment to the knee joint. The knee will initially be constrained at an initial angle of 15¿ via pretensioned quadriceps, medial and lateral hamstring and gastrocnemius muscle- equivalents, but the knee can flex under load. In AIM 1 we will test the hypothesis that a 2*BW impulsive force that applies valgus, internal or external axial rotation moments to the knee will increase peak ACL strain compared with a sagittally-symmetric loading involving an equivalent flexion-only moment. In AIM 2 we will test the hypothesis that superposition of the AIM 1 valgus and axial rotation moment components results in greater peak ACL strain than a flexion moment of similar magnitude. In AIM 3 the hypothesis will be tested that there is a higher risk for ACL rupture under a 4*BW impulsive loading with an out-of-sagittal plane loading component than with sagittally-symmetric loading. In AIM 4 we will test the hypothesis that peak ACL strain can be reduced by stretch of the hamstring muscle-equivalents as the knee flexes in response to impulsive loading. Pilot data suggest that such stretch can be induced when adequate hip flexion accompanies the knee flexion associated with a jump landing; absence of such stretch results in increased ACL strain. Three hypotheses will be tested using paired knees in a repeated measures design. Load transducers will be used to measure the 3-D impulsive loading above and below the knee, and muscle forces will be measured using load cells. 3-D kinematics of the femur and tibia will be measured using the Certus system. ACL relative strain will be measured using a differential variable reluctance transducer. Up to 120 cadaver knees will be used.